JP2013541477A - Wireless communication network for transportation safety system - Google Patents

Abstract

  In a network for a safety system within a transportation system, the transportation system includes a shaft and a car disposed within the shaft. The first wall node is at the first end of the shaft and the second wall node is at the second end of the shaft and communicates a safety message with the car. Each wall node comprises at least one radio transceiver connected to one or more antennas. Each car in the shaft comprises at least two radio transceivers connected to one or more antennas, the first transceiver of the car uses a first frequency, and the second transceiver of the car is Each safety message is duplicated and communicated using the second frequency. A wired backbone connects a set of wall nodes to the controller of the transportation system safety system.

Description

  The present invention relates generally to mobile radio networks, and more particularly to reliable communications used in secure transportation systems such as elevator systems.

  Communication in safety systems requires very high reliability and very low latency. Therefore, conventionally, communication is performed using a dedicated wired medium. For example, in an elevator system, a heavy communication cable is suspended in the shaft and moves with the car to send a safety message between the controller and the elevator car. As the height of the building increases, the weight and cost of the communication cable increases significantly. As the weight increases, the power consumption of the elevator system also increases. Building height has a synergistic effect on the total cost and power consumption of the elevator system. For safety systems in elevator systems, lower cost and more energy efficient solutions are desirable. A possible solution is to replace wired communication with wireless communication.

To ensure the safety of elevator passengers, the International Electrotechnical Commission (IEC) has strict safety requirements for elevator communication networks that allow only one error in 1000 trillion (10 ¹⁵ ) safety-related messages. And publish reliability requirements. However, wireless communications are subject to external interference and varying radio channel conditions. In addition, wireless communication has a limited transmission distance, especially in indoor settings. Therefore, it is very difficult to apply wireless communication to the safety system of an elevator system.

  Accordingly, it is desirable to provide a reliable wireless communication network that meets stringent safety and reliability requirements for elevators and other similar safety systems.

  Embodiments of the present invention provide a method and system for reliable wireless communication between a controller in an elevator system and a car. In particular, in a network for a safety system within a transportation system, the transportation system includes a shaft and a car disposed within the shaft.

  The first wall node is at the first end of the shaft and the second wall node is at the second end of the shaft and communicates a safety message with the car. Each wall node comprises at least one radio transceiver connected to one or more antennas.

  Each car in the shaft comprises at least two radio transceivers connected to one or more antennas, the first transceiver of the car uses a first frequency, and the second transceiver of the car is Each safety message is duplicated and communicated using the second frequency.

  A wired backbone connects a set of wall nodes to the safety system controller of the transportation system.

1 is a schematic diagram of an elevator safety system for a low-rise building with a single shaft and a single car in the elevator system. 1 is a schematic diagram of an elevator safety system for a low-rise building with a single shaft and two cars in the elevator system. 1 is a schematic diagram of an elevator safety system for a high-rise building with a single shaft and a single car in the elevator system. 1 is a schematic view of an elevator safety system for a high-rise building with a single shaft and two cars in the elevator system. It is a block diagram of the wall node of an elevator safety system. It is a block diagram of the car node of an elevator safety system. 3 is a flow chart of a downlink communication protocol with redundancy for an elevator safety system. FIG. 2 is a schematic diagram of frequency allocation and interference using two frequency channels in a building with multiple elevator shafts. FIG. 3 is a schematic diagram of frequency allocation and interference using four frequency channels in a building with multiple elevator shafts. It is the schematic of the shared backbone between several elevator shafts.

  Embodiments of the present invention provide a safety system using wireless communication for a transportation system, such as an elevator system. It should be understood that this safety system can be used in other transport systems that have stringent communication and safety requirements, such as mines and galleries, and underground or underwater transport tunnels. is there.

  Thus, as defined herein, a shaft is any relatively narrow and elongated enclosed space. Usually the shaft is longer than 20 meters. The shaft comprises one or more cages for transporting people or things. The cage can move horizontally or vertically within the shaft, or the shaft can be tilted. Conventional wireless communication is usually ineligible due to the length of the shaft and because each car can substantially fill the cross section of the shaft.

  The main concern of the present invention is the communication of safety messages between the car and the controller that controls the operation of the car in the shaft. Thus, any of the nodes can be a source or sink of safety messages.

  The system can be implemented for buildings having one or more elevator shafts and one or more elevator cars per shaft. Communication takes place between a car node located on the car, a set (one or more) of intermediate wall nodes located within the shaft, and the controller. The wall nodes and the controller are interconnected by a wired backbone. The car and car node are movable, while the wall node and controller are fixed in place. Each node comprises at least one radio transceiver connected to one or more antennas. A wireless transceiver is a transmitter and a receiver.

  For reliable communication, each car has at least two car nodes (transceivers). Additional car nodes can be used to increase reliability.

  The wall node serves as a relay node between the car node and the controller. A wired backbone can carry messages between a wall node and a controller in one shaft or in multiple adjacent shafts.

Low-rise building As shown in FIG. 1A, when the elevator system 101 is in the low-rise building 100, the elevator system serves only a small number of floors, and therefore the height of the service zone is below the radio transmission distance, Using two (hatched) wall nodes 300, a first wall node at the first (lower) end of the shaft and a second wall node at the second (upper) end of the shaft Can do.

The two antennas 105 of the car node 400 in the car 110 have one transceiver communicating with the top wall node using frequency f ₁ 121 and the second transceiver using the frequency f ₂ 122 to communicate with the bottom wall node. Arranged to communicate. It is preferred that f ₁ is separate from f ₂ , but since the frequency used depends on the actual radio technology, this is not a strict requirement unless the frequency causes significant interference in the vicinity of the receiver . A wired backbone 130 communicates between wall nodes.

The frequencies f ₁ and f ₂ can be in the millimeter wave band or in a band below 6 GHz (sub-6 GHz: sub 6 GHz), one frequency is selected from the millimeter wave band and the other is It is also possible to select from a band of less than 6 GHz.

  In the preferred architecture, both frequencies are selected from industrial, scientific, and medical (ISM) radio bands, such as 24 GHz or 60 GHz. Millimeter wave transmission is usually unaffected by interference emanating from the outside of the shaft and provides a narrow beam that can travel longer distances. Using a millimeter wave radio frequency with a transmission power of 10 dBm and a directional antenna with a gain of up to 30 dBi, only two wall nodes are required for a shaft up to 200 meters long. Conventional wireless safety systems are usually limited to shafts of less than 10 meters. For this reason, the length of the shaft is a major obstacle when using a conventional wireless network.

  Alternatively, a frequency such as 2.4 GHz or 5.8 GHz can be selected within a band of less than 6 GHz. However, external interference (from existing systems such as WiFi networks) is a problem at this time, and high gain antennas are usually larger and heavier. When there is no interference on the shaft, with sufficient transmit power and antenna gain, two wall nodes can be used in elevator shafts up to 100-200 meters high. Under worst case interference scenarios, these wall nodes can be used in elevator shafts up to 10 meters to 20 meters high.

Alternatively, the frequency f ₁ can be selected from the millimeter wave band and the frequency f ₂ can be selected from a band below 6 GHz.

  In a preferred embodiment, the interstory wired backbone 130 can be a riser-rise fiber optic cable. The cable has at least two fibers, the first fiber is for the downlink from the controller to the wall node, and the second fiber is for the uplink from the wall node to the controller.

  As shown in FIG. 1B, some elevator systems support two cars 210 and 211 that move independently within a single shaft. In this case, in a low-rise building, each node includes two radio wave transceivers 205. The top wall node of the shaft communicates with both antennas as to whether to serve the higher floors. Similarly, the bottom wall node of the shaft communicates with both antennas as to serving the lower floors.

High-rise building As shown in FIG. 2A, a high-rise building requires three or more wall nodes 300. Wall nodes are arranged linearly along the shaft or attached to the shaft rail. The wall nodes located at the top and bottom of the shaft have only one radio transceiver, and all other wall nodes have two transceivers. The backbone 130 interconnects the wall nodes with each other.

When the millimeter wave band is used for wireless communication, the antenna can have high directivity. The two antennas at each wall node point in the opposite direction, one is upward and the other is downward. All antennas pointing down the wall node use frequency f ₁ and all antennas pointing up the wall node use frequency f ₂ . In the car, an antenna pointing upwards communicates using frequency f _1, and an antenna pointing downwards uses frequency f ₂ . Using a millimeter wave band with a high gain antenna, the distance between wall nodes can be between 100 meters and 200 meters.

  FIG. 2B shows a similar architecture for a high-rise building with two cages in the shaft.

Node Configuration FIG. 3 shows the components and operation of the wall node 300. The wall node relays the following input / output (I / O) ports: the I / O interface 311 with the controller, the input port for receiving the downlink (DL) backbone signal 312, the downlink backbone signal 315. An output port for receiving an uplink (UL) backbone signal 314, an output port for relaying the uplink backbone signal 313, and two I / O ports to the radio transceiver 320.

  The wall node comprises a decoder 331, an encoder 332, a duplicator 340, a buffer and multiplexer 350, and a module 360 for processing uplink messages.

  A wall node can be configured as one of three node types: one at the beginning, one at the relay, and one at the end. As shown in Table 1, ports can be enabled or disabled depending on the node type allocation of wall nodes.

  When a port is disabled, one embodiment can choose not to install the relevant components in the actual device.

  When the wall node is adjacent to the controller, the node type is first. In this case, the node receives the DL message directly from the controller, so the node disables the input of the DL backbone signal 312. The leading node can choose to buffer and combine multiple DL messages to improve communication efficiency. This wall node can also send UL messages directly to the controller, thus invalidating the output for relaying UL messages through the backbone.

  The node type is terminal when the wall node is located at the furthest distance from the controller, eg at the bottom of the shaft when the controller is at the top of the elevator shaft. In this case, the node invalidates the output relaying the DL backbone 332 and invalidates the input of the UL backbone signal 314. The node also invalidates the I / O 311 to the controller.

  All other wall nodes are of the relay type. In this case, the node invalidates the I / O 311 to the controller. All DL messages are obtained from input from the DL backbone.

  In the case of the head node and the relay node, all DL messages are duplicated (340), relayed to the output of the DL backbone, and transmitted to the radio transceiver 320. In the case of a terminal node, the DL message is transmitted only to the radio transceiver 320.

  The output UL message is constructed based on signals received from the input UL backbone 314 and the wireless transceiver 320. The received signals of the two radio transceivers are processed (360) and then buffered and multiplexed (350) with the decoded backbone signal 331 received from the UL backbone.

  Although the wall node includes two I / O ports for the wireless transceiver, it is possible to configure the wall node so that only one of the transceivers is active. For example, the leading wall node can use only one radio transceiver for the case shown in FIGS. 1A, 2A, and 2B, or the leading wall node can be used for the case shown in FIG. 1B. Two transceivers can be used.

  As shown in FIG. 4, the car node 400 duplicates the uplink message 401 (410) and transmits the message to the two antennas 305 of the transceiver. The wireless transceiver 320 also receives the downlink message 402 and processes the message (420).

Redundant Transmission As shown in FIG. 5, to ensure reliability, signals are transmitted to the car via two independent radio paths, a primary path 561 and a redundant path 562. The DL message flows from the controller 501 to the car node 550 through two paths (solid lines), while the UL message flows from the car node 550 to the controller 501 through two paths (dashed lines). Assume that the car node is located somewhere between two wall nodes: wall node 520 and wall node 530. The controller passes the message to wall node 510 and the message is relayed to wall node 520. The wall node 520 duplicates each message, sends one copy to the wall node radio transceiver 521 and relays the other copy to the wall node 530. The wall node 530 proceeds in the same manner. The wall node 530 duplicates each message, sends one copy to the wall node radio transceiver 531 and relays another copy to the wall node 540.

  Both wall node radio transceivers 521 and 531 receive a copy of the DL message at different times. The wall node transmits the message wirelessly to the car node independently. In one path, called the primary path, the radio signal is transmitted from the wall node radio transceiver 521 to the car node radio transceiver 551. In another path, called a redundant path, the radio signal is transmitted from the wall node radio transceiver 531 to the car node radio transceiver 552. The car node then receives messages from both radio transceivers 551 and 552. The probability that a message will be successfully received via at least one path is higher than a design that uses only a single communication path, thus increasing reliability.

  During downlink transmission, after the wall node relays the message through the backbone, multiple wall nodes corresponding to the same path, eg, the primary path, transmit the message at the same time to avoid interference with each other. These transmissions using the same frequency channel are combined across the radio channel by natural laws. However, even if the signal travels at the speed of light, a slight difference in distance may cause the signals to be combined with a small time offset. The car node can either (1) decode the message by using the combined signal, or (2) perform evolved signal processing to select one of many paths and decode the message Can be.

  For clarity, the wall nodes corresponding to the primary path transmit at the same time, and the wall nodes corresponding to the redundant path transmit at the same time. On the other hand, the transmission of the primary path and the redundant path can be independent of each other.

  Note that a message can be retransmitted multiple times over the same channel, increasing the success probability of message reception and overall system reliability.

  Similarly, the UL message from the car node to the controller node is transmitted over two independent paths indicated by broken lines in FIG.

  During uplink transmission, when the car node transmits, multiple wall nodes can independently receive a copy of the transmitted signal. In this case, the wall node relays all received copies of the transmission to the controller.

Frequency Allocation for Multiple Shafts As shown in FIG. 6A, many buildings include an elevator system group in which multiple cars travel adjacent to each other in adjacent shafts. Typically, the shaft is placed in one large open space in the center of the building. That is, each shaft mainly includes a guide rail through which a car travels, and the rest is an open space. The adjacent shaft controller 101 is interconnected with the group controller 610.

  In an elevator system group, wireless communications between various nodes installed in adjacent shafts can interfere with each other (601). Frequency allocation can be used to improve performance.

In some countries, only two frequency channels are allowed for a particular radio frequency band. FIG. 6A shows frequency allocation in this case. When a shaft uses f ₁ for downward transmission (from the wall node) and f ₂ for upward transmission, the adjacent shaft reverses the use of two frequencies and uses f ₁ for upward transmission, using _{f 2} downward transmission. Note that in FIG. 6A, the transmissions of the two wall nodes can interfere with each other.

  The IEEE 802.11ad standard for wireless local area networks allows for additional frequencies. If four frequency channels can be selected in the frequency band, the frequency assignment can be changed to the assignment shown in FIG. 6B. Adjacent shafts use completely different frequencies, and the upper and lower frequency assignments are exchanged for adjacent shafts.

If the shared backbone backbone 130 (see FIG. 1) has a large capacity, it is possible to combine the functions of multiple backbones into one. Although additional protocol overhead is required to identify the source and destination of the message, the integrated backbone allows adjacent wall nodes to be combined to implement interference cancellation. Please refer to FIG.

Downward transmissions from both the car on one shaft and the wall node on the other shaft use frequency f ₂ 701 and the wall node serving the car receives the transmission on frequency f ₂ . The two transmissions cause interference with each other.

  On the other hand, with a shared backbone, transmissions of adjacent shaft wall nodes are transmitted over the same backbone. For this reason, transmission is known to the wall node on both shafts. The wall node can then use this information to cease wireless transmission from the adjacent wall node.

Claims (15)

A network for a safety system in a transportation system,
The transport system is a shaft and a car disposed within the shaft, the shaft being a relatively narrow and elongated sealed space, the shaft being fixed in place, and the car being the shaft The car is disposed within the shaft and substantially fills a cross-section of the shaft;
A set of wall nodes disposed within the shaft, each wall node being fixed in position, wherein the set of wall nodes is a first at a first end of the shaft; Including a wall node, a second wall node at the second end of the shaft, and another wall node in between as a relay node, each wall node connected to one or more antennas A set of wall nodes comprising at least one radio transceiver, each wall node being a source or sink of safety messages;
A set of car nodes disposed on the car, each car node comprising at least two radio transceivers connected to one or more antennas, each transceiver comprising a transmitter and a receiver Each car node can be the source or the sink of the safety message, the first transceiver uses a first frequency, and the second transceiver uses a second frequency. A set of car nodes that replicate and communicate each safety message using
A wired backbone connecting the set of wall nodes to a controller of the safety system of the transportation system;
A network for a safety system in a transportation system comprising: The frequency is selected within industrial, scientific, and medical (ISM) radio bands,
The network according to claim 1. The backbone includes at least two fibers, a first fiber for the downlink from the controller to the wall node and the second fiber for the uplink from the wall node to the controller. Optical fiber cable,
The network according to claim 1. The length of the shaft is substantially greater than 10 meters;
The network according to claim 1. The shaft includes a plurality of independently moving cages,
The network according to claim 1. The distance between the first wall node and the second wall node is greater than 100 meters;
The network according to claim 1. The transportation system includes a plurality of shafts, each shaft including one or more cages;
The network according to claim 1. Each wall node replicates a downlink backbone signal so that the signal is communicated to all radio transceivers and the signal is relayed to another wall node via the backbone,
The network according to claim 1. Both downlink and uplink signals are transmitted and received over at least two independent radio channels.
The network according to claim 1. Each safety message from the controller is retransmitted simultaneously by multiple wall nodes, and each car node decodes the safety message by combining all the received safety messages.
The network according to claim 1. Each safety message from the controller is retransmitted simultaneously by a plurality of wall nodes, and each car node decodes the safety message by selecting one of the received safety messages.
The network according to claim 1. A transmission from each car node is received by a plurality of wall nodes, which transmit all received copies to the controller via the backbone.
The network according to claim 1. The backbone connects the wall nodes in the plurality of shafts;
The network according to claim 7. The frequency is selected at 24 GHz, 25 GHz, or 60 GHz within the millimeter wave band.
The network according to claim 2. The frequency is selected at 2.4 GHz or 5.6 GHz within a band of less than 6 GHz.
The network according to claim 2.

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